Prior art cutting units often comprise a cutting drum and an anvil drum. These are arranged on arbours, which are rotatable supported in a frame by bearing blocks. The cutting drum and the anvil drum are arranged one over the other with their arbours and axis of rotation extending horizontal and in parallel. In the prior art cutting units are known, where the cutting drum is arranged over the anvil drum, and cutting units, where the anvil drum is arranged over the cutting drum. Normally at least one of the drums is connected to a driving device for rotating the arbour with the drum.
Cutting units are normally used for continuously cutting web material fed between the upper and the lower drum. The cut articles and the trim are evacuated by for example conveyors and vacuum nozzles.
A known type of cutting unit has hydraulic, extendable cylinders that bear between the frame and the lower drum to press it against the upper drum for affecting the desired cutting pressure. To this end, the bearing blocks of the lower drum are movable arranged on linear guides, while the bearing blocks of the upper drum are fixed in the frame.
After the cutting unit has been run a certain time, the cutting drum and the anvil drum have to be reground. A problem with regrinding is that in order to obtain desired cutting depth and cutting force during use, the cutting portions and anvil portions of the drums have to be strictly concentric in combination with an exact centring of the drum on the arbour and in the bearing blocks, which requires a very exact regrinding operation. In addition, the drums have to be removed from the cutting unit in order to carry out regrinding. This is a rather complex and time consuming operation, especially for the lower drum, which is more difficult to access below upper drum.